The neck of a person lying in a supine or sidelying position is often out of alignment with the person's spine. This is commonly the case when the person's neck is supported by a pillow or multiple pillows such that the neck lies at an angle defined by the deflected height of the pillow(s), and this angle is typically not co-planar with the spine. The deflected height of the pillow is closely related to its stiffness, which is conventionally provided by filling material disposed within a fabric covering. Conventional filling material can include feathers, cotton, or a synthetic filler.